gen-cam-menu: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/gen-cam-menu - from package: feh

You may install the required package with command apt-get install {package}

Error in other languages:
gen-cam-menu: bevel nie gevind nie
gen-cam-menu: comandă negăsită
gen-cam-menu: comando não encontrado
gen-cam-menu: commande introuvable
gen-cam-menu: command not found
gen-cam-menu: käsku ei ole
gen-cam-menu: không tìm thấy lệnh
gen-cam-menu: komanda nerasta
gen-cam-menu: Kommando nicht gefunden.
gen-cam-menu: kommandot finns inte
gen-cam-menu: komut yok
gen-cam-menu: nie znaleziono polecenia
gen-cam-menu: níor aimsíodh an t-ordú
gen-cam-menu: no se encontró la orden
gen-cam-menu: no s'ha trobat l'ordre
gen-cam-menu: opdracht niet gevonden
gen-cam-menu: parancs nem található
gen-cam-menu: perintah tidak ditemukan
gen-cam-menu: príkaz nenájdený
gen-cam-menu: příkaz nenalezen
gen-cam-menu: команда не найдена
gen-cam-menu: командата не е открита
gen-cam-menu: 命令找不到
gen-cam-menu: コマンドが見つかりません